Strike Industries M-LOK AR15 Strike Rail - 15.5in - Red - The SI Strike Rail for the AR-15 was developed to fulfill the requirements of certain agency partners, who wanted a lightweight, but feature packed rail that they could depend on when entering harm's way. In service of this mission, we bring to you, the new SI Strike Rail. Lightweight, high strength, everything you need, and nothing you don't. Features Made in the USA ; 1.57 inch internal Diameter for suppressor or Oppressor compatibility; 1.80 inch outer width from flat end to flat end; For AR-15 style rifles only; Ambidextrous QD socket placement; Built in anti rotation feature in rail; Reinforced Steel Mounting Nut and Bolt;